Work is proposed on the following topics: The origin circulation and fate of synaptic vesicle membranes and of outer segment membranes in frog retinal photoreceptors; this will be based on cytochemical demonstration of endogenous enzymes and other components and on the use of horseradish peroxidase to follow endocytic processes; The effects of divalent cations, aspartate and varying illumination conditions on synaptic acitivity of photoreceptors and other neurons in the frog retina; this will be based on use of peroxidase uptake as an index to synaptic activity, and on extracellular recording procedures; Immunohistochemical and physiological studies of the binding of antibodies to acetylcholine receptor to electroplax of Electrophorus and to subcellular fractions prepared from electroplax of Torpedo; Cytochemical methods (usual methods for catalase and currently new ones for oxidases) for study of peroxisomal enzymes will be applied to myelinating nervous tissue in culture and to brain of adult and newborn rats treated with drugs know to affect hepatic peroxisomes, and to alter lipid metabolism; Work will continue on density gradient purification of intracellular granules from epithelial cells of the toad bladder and on evaluation of the role of these granules in permeability changes. BIBLIOGRAPHIC REFERENCES: Holtzman, E. 1977. The origin and fate of secretory packages, especially synaptic vesicles. Neuroscience (in press). Holtzman, E., Karlin, A., Valderrama, R. and Reyes, F. 1977. Immunocytochemical localization of acetylcholine receptors in Electrophorus electroplax. J. Histochem. Cytochem. 25:241 (abstract).